Sorry, I'm a little late to the party. Not sure whether it's good or bad, but I often come up with data that can't be verified.
Still, there are some ways to check how accurate it is:
- There was a 'MyPS4Life leak', and actually the whole site is built around it. Here's a comparison of gamstat.com estimates with the MyPS4Life figures (my estimates could've changed a little since then).
- Once a quarter Sony is reporting the number of PS+ subscribers. I calculate my own number, and if it matches the figure reported by Sony (so far it does) - it means I'm calculating the total number of PSN accounts right - and it's the most important number for calculations.
- Famitsu's estimates. They usually report a bigger number of sales in Japan than I do, and I'm not sure if it's my underestimation - or their overestimation. (Or offline players, or slow 'sales into players' conversion or whatever).
- GT Sport website, which includes a full list of all players. My player count estimate is ~10% higher, and as for regions - the comparison says that I might generally underestimate Germany, Japan and Italy, and overestimate France and Russia - https://twitter.com/GamstatC/status/1248034534190452737
So you can't just throw away my estimates ('not accurate at all', 'estimates out of ass'). Especially considering that the usual alternative is having no data at all.
You should treat these data with a grain a salt, of course, but - based on all the information I have - they are pretty accurate and should give you an overall picture.
If you can point me to other real data for a sanity check - I'm all ears.